Transistorized ignition apparatus



Feb. 21, 1967 c. E. MAIDEN ETAL 3,304,926 TRANSISTORIZED IGNITION APPARATUS Filed May 7, 1964 8 34 FM]. 2 40%44 M 66 Fig. 4.

M i n dougos E. Gedguudos,

Clinron E. Maiden,

INVENTORS.

ATTORNEY.

United States Patent 3,304,926 TRANSISTORIZED IGNITION APPARATUS Clinton E. Maiden, Canoga Park, and Mindangas E.

Gedgandas, Inglewood, Calif, assignors to Clinton- Angis Company, Canoga Park, Calif.

Filed May 7, 1964, Ser. No. 365,706 4 Claims. (Cl. 123-148) This invention relates to the ingition system of an internal combustion engine of the electrical spark ignition type. More particularly, the invention relates to apparatus including semiconductor components for developing and applying the electrical voltage to the spark plugs in an internal combustion engine.

Internal combustion engines may conveniently be grouped into two major classes: the explosive or socalled Otto cycle type wherein a volatile fuel is exploded by means of an electrically produced spark; and the nonexplosive type wherein a fuel, which may be less volatile, is caused to burn by means of compression. An example of the first type is the well-known gasoline internal combustion engine employed in most automobiles. The present invention appertains to the first type which, for convenience, is hereinafter identified as a spark-ignited internal combustion engine.

In the explosive ignition type engine an electrical spark is caused to form across the gap between the two electrodes of what is called a spark plug by impressing a high voltage on these electrodes which are disposed in the combustion chamber or cylinder. The high voltage is usually developed by means of an induction coil commonly referred to as the spark coil which is connected series-wise in circuit with a voltage source and the spark plug electrodes. In engines having more than one combustion chamber or cylinder it is necessary to switch the spark voltage from one spark plug electrode to another in a predetermined timed firing order. Such switching or distribution of the ignition voltage is usually accomplished by means of a mechanically rotating commutator or brush arrangement called a distributor having a contact shaft coupled to the main drive shaft of the engine whereby the rotation of the distributor contact closes the circuit between each spark plug and the spark coil in a predetermined timed sequence, there being provided a discrete contact element in the distributor for each plug to be fired which is physically and electrically contacted by the rotating distributor contact.

It is well known that a voltage distribution system leaves much to be desired in the way of optimum engine performance. Most of the difiiculties with such a distribution system lie in the necessity of mechanically switching a very high current high voltage across the contacts in the distributor. During use the contacts tend not only to wear physically but also to oxidize or otherwise become corroded which is enhanced considerably by the high currents and voltages involved. Most ignition troubles in the modern spark ignition internal combustion engine find their basis in the ignition distribution system. Thus, the wear and corrosion of the distributor contacts tend to dissipate energy at the contact points so that nonuniform voltages are applied to different spark plugs which not only causes the development of non-uniform mechanical power from cylinder to cylinder but also is a contributing factor to fouling of the spark plug points or electrodes. Eventually the combination of varying firing voltages and spark plug fouling combine so that combustion in a given cylinder is incomplete or even fails to occur altogether. Eventually the distributor contacts themselves become so poor through Wear and corrosion that they must be periodically replaced as is well known to all operators and owners of modern automobiles.

With the discovery and development of such semiconductor electronic devices as the diode and transistor much attention has been focused upon the possibility of utilizing these devices in the ignition distribution system just-described so as to avoid the aforementioned problems. The usefulness of such semiconductor components in such a system is readily apparent when it is considered that the transistor, for example, is nothing more than a solid state electrical switch with no moving parts. Many arrangements have been proposed for utilizing semiconductor devices to avoid the switching of high voltages across moving electrical contacts.

However, in marrying todays spark-ignited internal combustion engines with a semiconductor or transistorized ignition system one of the serious problems encountered is the high ambient temperatures existing in the engine compartment in most automobiles and trucks which may range from 65 to 85 C. or more. It is well known that the operation of semiconductor devices utilizing germanium or silicon materials is subject to rather severe maximum temperature limitations. The temperature limitation of a typical semiconductor device is determined primarily by the energy gap between the valence bands and the conduction bands of the semiconductive material employed. When the temperature of the device reaches a point where the thermal energy is sufficient to raise substantial members of electrons across the energy gap, the semiconductive characteristics of the material are adversely affected. For example, the energy gap of germanium is about 0.7 electron volt and many devices using germanium become inoperative above temperatures as low as C. Hence, all of the presently known transistorized ignition schemes on the market prior to the present invention circumvent the temperature problems by providing the electronic semiconductive circuit portion of the ignition system in a separate package and locating this package on a heat sink as remotely as possible from the rest of the ignition system and the internal combustion engine. Such an arrangement requires the individual handling and mounting of several different assemblies or components as well as the costly and timeconsuming job of providing the necessary electrical connections 'therebetween. In general, the transistorized ignition system of the type to which the present invention appertains includes a spark coil, an electronic circuit, and a ballast resistor together with such necessary hard ware as wires, nuts, bolts, terminals and the like. In the aforementioned transistorized ignition systems on the market these items are separately installed and mounted at different locations as indicated.

It is therefore an object of the present invention to provide an improved transistorized ignition system for spark-ignited internal combustion engines.

Another object of the invention is to provide an improved unitized transistorized ignition apparatus for spark-ignited internal combustion engines.

Another object of the invention is to provide an improved unitized transistorized ignition apparatus which may be mounted in a single installation on an internal combustion engine of the spark-ignited type.

Still another object of the invention is to provide an improved unitized transistorized ignition apparatus which may be readily installed on an internal combustion engine of the spark-ignition type with a minimum number of electrical connections.

Yet another object of the invention is to provide an improved transistorized ignition apparatus which is integral with a conventional component of an ignition system for a spark-ignited internal combustion engine.

Another object of the invention is to provide an improved transistorized ignition apparatus which may be mounted in an engine compartment with an engine of the internal combustion type and not damaged or otherwise adversely affected by the temperatures therewithin.

These and other objects and advantages of the invention are realized by mounting an electronic transistor circuit for an ignition system within and on a heat dissipating member which is integral with the ignition spark coil of the ignition system of an internal combustion engine of the spark-ignited type. Thus in order to adapt an existing ignition system with the transistorized ignition apparatus of the present invention, it is only necessary to replace the existing spark coil with the spark coil electronic transistor circuit combination of the present invention while utilizing the existing wiring connections and distributor. As used herein when reference is made to the transistorized ignition system or apparatus of the present invention, it is not intended to mean thereby a complete ignition system including distributor and spark plugs. Nor is the term transistorized intended to preclude the use of other semiconductive components such as diodes or rectifiers and the like either in addition to or in place of three or four element semi conductor devices such as transistors and silicon controlled rectifiers.

The invention will be described and its operation explained in greater detail by reference to the drawings in which:

FIGURE 1 is an elevational view, partly in section, showing the transistorized ignition apparatus of the present invention;

FIGURE 2 is a plan view of the top of the apparatus shown in FIGURE 1 taken along the line 2-2 thereof;

FIGURE 3 is a plan view of the bottom of the apparatus shown in FIGURE 1 taken along the line 3-3 thereof; and

FIGURE 4 is a schematic circuit diagram of the transistorized ignition apparatus of the present invention.

Referring now to the drawings and to FIGURE 1 in particular, there is shown a unitized transistorized apparatus 2 according to the present invention comprising a spark coil-containing member 4 and a hollow heat dissipating member 6 containing therewithin an electronic circuit assembly 8. The spark coil member 4 may be of any conventional oil or tar-fi11ed type such as is usually found installed on the internal combustion engine in an automobile. Such coils comprise an induction coil (not shown) mounted in a cylindrical can-shaped jacket having a terminal 16 at one end thereof which is adapted to be connected to the high-voltage wire which is, in turn, connected to the central, or common, terminal of the distributor. The coil member 4 is also provided on its upper end as viewed in the drawings with a pair of terminal lugs 12 and 14 which are in turn connected to respective inductance coils within the coil member 4.

According to the present invention the spark coil member 4 is provided with an exterior jacket or coating 16 of a suitable thermosetting plastic such as an epoxy. In practice the plastic jacket 16 may be provided by simply applying the plastic in its uncured and liquid phase to a conventional spark coil member 14- as by immersing the coil member in the liquid plastic so that all desired surface areas thereof are coated therewith and then curing the plastic as by heating, for example.

Secured around the outside of the coil member 4 is a mounting band member 18 which is intended to support a ballast resistor 19 which is connected between ground and the coil terminal lug 12 by means of a wire 20 which extends from the lug 12 through a hole drilled in the plastic jacket 16 from the upper surface of the coil member 4 to an outside wall surface thereof as represented by the dotted lines 20 in FIGURE 1.

Mounted on the upper end of the spark coil member 4 is a heat dissipating member 6 in the form of a hollow metallic cylinder whose outer surface is provided with a plurality of fins 22 and grooves 24 so as to provide a substantially large surface area to the atmosphere for dissipation of heat from the interior thereof. The inside diameter of the metallic cylinder 6 is such as to insure a relatively tight fit around the top of the coil member 4. The inside surface 28 of the heat dissipating cylinder member 6 is provided with a shoulder portion 26 by making the inside diameter of this upper portion somewhat larger than the inside diameter of the lower portion thereof. In addition, the inside surface 28 of this upper portion of the cylindrical member 6 is provided with .an inside taper whereby the inside diameter of the upper portion becomes progressively smaller as the shoulder portion 26 is approached.

Mounted within the heat dissipating member 6 is a circular mounting plate 30 which may also be of metal. The diameter of the mounting plate 30 is such with respect to the progressively smaller inside diameter of the upper portion of the cylindrical member 6 that the plate 30 may be pushed down into the interior of the cylindrical member 6 into an extremely tight fit therewith on the top surface of the shoulder portion 26. Both finned heat dissipating member 6 and the mounting plate 30 may be formed of any good thermally conductive, preferably non-corrosive metal such as aluminum, for example. The electronic components for the transistorized ignition system of the invention are mounted on both the upper and lower surfaces of the mounting plate by means of solder connections and/ or mounting strips and lugs such as 32 and 34, for example, which are secured to the mounting plate 30 by means of nuts 36 and 38.

Referring now to FIGURES 2 and 3 in particular, a resistor 40, a thermal switch 42, and a transistor device 44 in a conventional metallic package are disposed on the upper surface of the mounting plate 30. The resistor 40 is mounted by securing one of its leads to the terminal lug 34, for example, and soldering its other lead to the connecting tab 46 of the terminal switch 42. The other connecting tab 46 of the thermal switch 42 is extended over the hole 48 on the mounting plate 30 and is connected by a wire 46" to the base connection lead 50 of the transistor device 44 which lead extends through a hole in the mounting plate 30 to the bottom surface thereof. The transistor device 44 is of the collector stud mounting type which means that the electrical connection to the collector. region thereof is provided by a re1atively heavy centrally disposed threaded stud member which also permits mounting of the transistor device. Such transistor devices are well known and it is not believed that further description thereof is required herein. Typically suitable transistors for purposes of the present invention are the 2N1100 or the 2N1970, for example. Thus, the transistor device 44, by means of an insulating washer 52 and its stud lead 54 is mounted on the upper surface of the mounting plate in good thermally conductive relationship therewith with its leads extending through holes in the mounting plate for connection thereto from beneath the mounting plate.

It will be appreciated that the thermal switch 42, which is a conventional temperature responsive switch which opens a circuit if the ambient temperature reaches or exceeds some predetermined point, may be dispensed with if such protection is not desired. It should be noted that the utilization of this switch to protect the transistor device 44- also results in additional protection against discharging the storage battery in an automobile by leaving the ignition turned on without the motor running. Under such conditions, the switch may be set to open the ignition circuit upon the attainment of some predetermined temperature due to the heat generated in the nearby electrical components.

With particular reference to FIGURES 1 and 3, on the under side of the mounting plate 30 a semiconductor diode device 56 of the stud mount type is mounted through a hole in the mounting plate in good thermal conducting relationship therewith. The threaded stud 58 of this diode extends through the mounting plate and is secured thereto by means of the nut 58' shown in FIGURE 2. Typical examples of a suitable diode for the purposes of the present invention are those designated in the industry as a 1N1372 or a 1N3002A. The diode 56 may be electrically insulated from the mounting plate 30 by means of washers 59 and 59'. The diode is also connected by means of a connecting strip 60 to the collector electrode 54 of the transistor device 44.

Also disposed on the under side of the mounting plate 30 are a resistor 62 and a capacitor 64. The resistor element 62 is secured by soldering its lead wires to the base connection lead 50 and to the emittercounection lead 51 of the transistor 44. The capacitor element 64 is likewise secured by soldered connections'to the lug 32 and to the connecting strip 66 as shown in FIGURE 3.

After the electrical circuit, as just described, has been mounted on the mounting plate 30, this plate is inserted down into the heat radiating cylinder 6 so as to finally rest on the internal shoulder portion 26 thereof in good heat conducting relationship. Thereafter the entire internal cavity within the cylinder 6 is filled with a thermosetting plastic material 66 such as the epoxy resin used to encase the spark coil member 4 previously. The cavity both above and below the mounting plate 30 is thus filled, the uncured and liquid plastic material flowing down into the cavity under this plate through the openings provided therein. The assembly is then baked for two hours at a temperature of 40 C., for example, to set and harden the plastic. Upon the hardening of the plastic it will be found that an extremely rugged assembly has been form-ed with the heat radiating cylinder 6 and its internally contained electronic circuit 8 strongly wedded to the spark coil member 4 so as to make the assembly an integral unit. The electronic circuit 8 is not only securely mounted in place and very effectively protected against the deleterious effects of vibration, moisture, dirt, grease and the ambient temperature by the plastic material 66 but is also in good conducting relationship with the heat radiating cylinder 6. Thus, by simply mounting the spark coil-transistorized electronic circuit combination of the present invention in place of the conventional spark coil on an internal combustion engine and making the appropriate wire connections, a transistorized ignition system is achieved.

While the present invention may be practiced with any kind of transistorized ignition system, a typical transistor circuit for use therein is shown in FIGURE 4 whose components have been described for purposes of illustration in FIGURES 1 through 3. With particular reference to FIGURE 4, a voltage and current source may be connected to the ground and the terminal 32 which in turn is connected to the spark coil terminal 14. This latter connection to the spark coil terminal 14 is not shown for the sake of clarity in the drawings. Because of the property of the transistor 44 to act as an open switch when no current flows in its base circuit, no current flows in the circuit when the distributor breaker points are open. However, when the engine turns over as during starting, the distributor cam rotates so as to close the mechanical breaker points thereof. At this time current starts flowing in the base circuit of the transistor and biases the transistor so that it turns on and allows a large current to flow from the battery through the terminal 32, the transistor 44, the primary winding of the spark coil 4, and the ballast resistor 159 to ground. The purpose of the ballast resistor is to limit the current to a desired value. The flow of this current establishes a magnetic field in the spark coil 4 so that when the current flow in the base circuit ceases, as when the distributor cam rotates further and again opens the breaker points, the collapse of the magnetic field in the spark coil 4 induces a large voltage in the secondary winding which appears at terminal 10. The collapse of the magnetic field also induces a back voltage in the primary winding which may reach a value greater than the blocking ability of the transistor which would thus damage this component. To prevent such damage, the Zener diode 56 is connected across the transistor. The diode is selected so as to have a breakdown voltage which is safe for the transistor and to thus channel the excess voltage supply around the transistor. As soon as the high voltage peak subsides, the Zener diode 56 will revert to its original blocking state to all voltages below its breakdown voltage. In order to further protect the transistor, the resistor 40 and the capacitor 64 are provided so as to limit current in the base circuit of the transistor and to store any high voltage, very short duration pulses which may be dissipated by the diode 56. In order to substantially increase the speed at which the transistor switches off and to also increase its ability to withstand high voltages, resistor 62 is provided which essentially short circuits the base lead to the emitter when the distributor breaker points are Open.

As mentioned previously the temperature sensitive switch 42 is provided to prevent the transistor 44 from becoming operative if the temperature surrounding it and the temperature sensitive switch exceeds a predetermined value. On the opening of the temperature sensitive switch 42, the electrical circuit as well as the internal combustion engine are rendered inoperative. The temperature sensitive switch may be connected between terminal 32 and the emitter lead of the transistor or anywhere between the collector lead and ground. In this latter case, the circuit may still continue heating after the temperature sensitive switch has opened due to the fact that the circuit between the breaker points of the distributor and the terminal 32 is still intact.

There thus has been described a novel transistorized ignition system in combination with a spark coil member for internal combustion engines of the spark ignition type.

What is claimed is: p

1. In an internal combustion engine of the spark ignition type, electrical ignition apparatus comprising, in combination:

(A) a spark coil member for developing a high voltage discharge;

(B) a thermo-setting plastic casing for said spark coil member;

(C) a heat-radiating casing aflixed to said casing for said spark coil member and including:

(1) a finned external wall;

(2) and a thermally conductive mounting plate affixed to said casing and in good thermally conducting relationship with said finned wall;

(D) a temperature sensitive electronic circuit disposed in said heat-radiating casing including electrical components affixed to and in good thermally conducting relationship with said mounting plate, and electrically connected to said spark coil member for controlling said high voltage discharge;

(E) and a thermo-setting plastic filling in said heatradiating casing surrounding said mounting plate and said electronic circuit and bonded to portions of said thermo-setting plastic casing for said spark coil member.

2. In an internal combustion engine of the spark ignition type, electrical ignition apparatus comprising, in combination:

(A) a spark coil member for developing a high voltage discharge;

(B) a thermo-setting plastic casing for said spark coil member;

(C) a heat-radiating casing afiixed to said casing for said spark coil member and including:

( l) a finned external wall;

(2) and a perforated thermally conductive mounting plate disposed in said heat-radiating casing in good thermally conductive relationship with said finned wall and dividing the interior of said heat-radiating casing into a pair of chambers one 7 of which faces the end of said spark coil memmember;

(D) a temperature sensitive electronic circuit disposed in said heat-radiating casing including electrical components distributed in said chambers and afiixed to said mounting plate in good thermally conducting relationship, and electrically connected to said spark coil member for controlling said high voltage discharge;

(E) and a thermo-setting plastic disposed in saidheatradiating casing and filling said chambers and bonded to said end of said spark coil member.

3. In an internal combustion engine of the spark ignition type, electrical ignition apparatus comprising in combination:

(A) a spark coil member for developing a high voltage discharge;

(B) a heat-radiating casing aifixed to and extending from said spark coil member and including:

(1) a finned external wall;

(2) and a thermally conductive mounting plate afiixed to said casing and in good thermally conducting relationship with said finned Wall;

(C) a temperature sensitive electronic circuit disposed in said heat-radiating casing including electrical components afiixed to and in good thermally conducting relationship with said mounting plate, and electrically connected to said spark coil member for controlling said high voltage discharge;

(D) and a thermo-setting plastic filling said heat-radiating casing surrounding said mounting plate and said electronic circuit and bonded to said spark coil member.

4. In an internal combustion engine of the spark ignition type, electrical ignition apparatus comprising in combination (A) a spark coil member for developing high voltage discharge;

(B) a heat-radiating casing affixed to and extending from said spark coil member and including:

(1) a finned external wall;

(2) and a perforated thermally conductive mounting plate disposed in said heat-radiating casing in good thermally conductive relationship with said finned wall and dividing the interior of said heat-radiating casing into a pair of chambers one of which faces the end of said spark coil member;

(C) a temperature sensitive electronic circuit disposed in said heat-radiating casing including electrical components distributed in said chambers and affixed to said mounting plate in good thermally conducting relationship, and electric-ally connected to said spark coil member for controlling said high voltage discharge;

(D) and a thermo-setting plastic disposed in said heatradiating casing and filling said chambers and bonded to said end of said spark coil member.

References Cited by the Examiner UNITED STATES PATENTS 2,383,735 8/1945 Ray.

2,737,579 3/1956 Wehrlin et al 174-355 2,832,012 4/1958 Kleason et a1 31710O X 3,171,046 2/ 1965 Meland.

4/1965 McKendry. 

1. IN AN INTERNAL COMBUSTION ENGINE OF THE SPARK IGNITION TYPE, ELECTRICAL IGNITION APPARATUS COMPRISING, IN COMBINATION: (A) A SPARK COIL MEMBER FOR DEVELOPING A HIGH VOLTAGE DISCHARGE; (B) A THERMO-SETTING PLASTIC CASING FOR SAID SPARK COIL MEMBER; (C) A HEAT-RADIATING CASING AFFIXED TO SAID CASING FOR SAID SPARK COIL MEMBER AND INCLUDING: (1) A FINNED EXTERNAL WALL; (2) AND A THERMALLY CONDUCTIVE MOUNTING PLATE AFFIXED TO SAID CASING AND IN GOOD THERMALLY CONDUCTING RELATIONSHIP WITH SAID FINNED WALL; (D) A TEMPERATURE SENSITIVE ELECTRONIC CIRCUIT DISPOSED IN SAID HEAT-RADIATING CASING INCLUDING ELECTRICAL COMPONENTS AFFIXED TO AND IN GOOD THERMALLY CONDUCTING RELATIONSHIP WITH SAID MOUNTING PLATE, AND ELECTRICALLY CONNECTED TO SAID SPARK COIL MEMBER FOR CONTROLLING SAID HIGH VOLTAGE DISCHARGE; (E) AND A THERMO-SETTING PLASTIC FILLING IN SAID HEATRADIATING CASING SURROUNDING SAID MOUNTING PLATE AND SAID ELECTRONIC CIRCUIT AND BONDED TO PORTIONS OF SAID THERMO-SETTING PLASTIC CASING FOR SAID SPARK COIL MEMBER. 